The present invention is directed to epoxidation of olefins using a mixture of a ketone and hydrogen peroxide.
Epoxidation of an olefin is one of the most useful synthetic reactions in the field of organic chemistry. Such reaction has been used frequently in the preparation of an intermediate and/or the final product of many pharmaceutically active compounds. With the recognition of the importance of a compound""s stereochemistry in its pharmaceutical activity, chiral epoxidation of an olefin has become particularly desirable.
Asymmetric epoxidation of olefins presents a powerful strategy for the synthesis of enantiomerically enriched epoxides. Great success has been achieved in the epoxidation of allylic alcohols, unfunctionalized cis-olefins, and conjugated trisubstituted olefins. Among many other powerful epoxidation methods chiral dioxiranes generated in situ from Oxone(copyright) (potassium peroxymonosulfate) and a chiral ketone have appeared to be promising reagents for asymmetric epoxidations. Since the first asymmetric epoxidation of olefins with dioxirane were reported in 1984, significant progress has been made in the area. A C2 symmetric cyclic chiral ketone derived from 1,1xe2x80x2-binaphthyl-2,2xe2x80x2-dicarboxylic acid has been used as a catalyst to achieve high enantioselectivity for the epoxidation of trans-4,4xe2x80x2-disubstituted stilbenes. Variety of other chiral ketones have been disclosed by others, for example, see Denmark and Wu, Synlett. 1999, 847, which is incorporated herein by reference in its entirety. Recently, the epoxidation of trans-disubstituted or trisubstituted olefins with high enantiomeric excess has been reported in commonly assigned PCT Publication No. WO 98/15544, which is incorporated herein by reference in its entirety.
As mentioned above, typically epoxidation of an olefin using a ketone and an oxidizing agent uses Oxone(copyright) as the oxidizing agent. The active component of Oxone(copyright) is believed to be potassium peroxymonosulfate. However, Oxone(copyright) contains other non-active salts. Often, these non-active salts must be removed after the epoxidation reaction, thereby increasing the time and cost of purifying the epoxide product. Moreover, typically an epoxidation reaction using a ketone and Oxone(copyright) requires a large volume of solvent.
Therefore, there is a need for a method of epoxidizing an olefin using a ketone and an oxidizing agent which does not require a large volume of reaction solvent. There is a need for a method of epoxidizing an olefin using a ketone and an oxidizing agent which does not require the use of Oxone(copyright). There is also a need for a method of epoxidizing a variety of olefins using a ketone and an oxidizing agent which does not contain a significant amount of non-active salt impurities.
Present invention provides a method for producing an epoxide from an olefin. The method involves mixing a reaction mixture comprising the olefin, hydrogen peroxide, a nitrile compound and a ketone under conditions sufficient to produce the epoxide.
The reaction mixture can also include a base. The pH of the reaction mixture is preferably from about pH 5 to about pH 14, more preferably at pH of from about pH 10 to about pH 14, and most preferably from about pH 10 to about pH 12.
In one particular embodiment of the present invention, the ketone is a chiral ketone which allows stereoselective epoxidation of the olefin. Preferably, the chiral ketone is selected from the group consisting of compounds of the formula: 
wherein
W, X, Y and Z are independently CR9R10, O, NR11, S, Se, Si or P;
l, m, n and p are independently an integer from 0 to 3;
R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are independently hydrogen, halide, hydroxyl, nitro, thio, or alkyl, alkoxy, aryl, silyl, siloxy, carbonyl, carboxylate, ester, amino, sulfinyl, sulfonyl, sulfate, sulfite, phosphate or phosphite groups containing from 1 to about 20 carbon atoms, or two or more of R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are linked together to form 3 to about 10 membered cyclic moiety containing 1 to about 20 carbon atoms; and
R11 is hydrogen, oxygen or alkyl, sulfonyl, alkoxy or carbonyl groups containing from 1 to about 20 carbon atoms.
More preferably, the chiral ketone is selected from the group consisting of the compound of the formula: 
wherein preferably, m is 0, Y is O or CR9R10, n and p are 1, and Z is CR9R10.
Preferably, two or more of R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are linked together to form 3 to about 10 membered cyclic moiety containing 1 to about 20 carbon atoms, more preferably R1 and R2 together form a moiety of the formula: 
xe2x80x94Oxe2x80x94C(CH2CH3)2xe2x80x94Oxe2x80x94CH2xe2x80x94 or xe2x80x94Oxe2x80x94C(CH3)2xe2x80x94Oxe2x80x94CH2xe2x80x94.
Alternatively, R1 and R7 together form a moiety of the formula:
xe2x80x94Oxe2x80x94C(CH3)2xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94C(CH2CH3)2xe2x80x94Oxe2x80x94, or xe2x80x94C(CH3)2xe2x80x94.
Preferably, R3 and R6 together form a moiety of the formula:
xe2x80x94Oxe2x80x94C(CH3)2xe2x80x94Oxe2x80x94or xe2x80x94Oxe2x80x94C(CH2CH3)2xe2x80x94Oxe2x80x94.
Preferably, R4, R5, R9 and R10 are independently hydrogen, halide or alkoxy, carboxyl or alkyl groups having 1 to about 20 carbon atoms. More preferably, R4, R5 and R10 are hydrogen and R9 is hydrogen, halide, or alkoxy, carboxyl, sulfinyl or alkyl groups having 1 to about 20 carbon atoms.
Preferably, the chiral ketone is derived from a carbohydrate, quinic acid or carvone. More preferably, the chiral ketone is derived from a group consisting of carvone, inositol, quinic acid, (D)-fructose, (L)-fructose, (D)-arabinose, (L)-arabinose and (L)-sorbose.